os_map.c
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上传日期:2022-05-23
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文件大小:11k
- /*-
- * See the file LICENSE for redistribution information.
- *
- * Copyright (c) 1996-2002
- * Sleepycat Software. All rights reserved.
- */
- #include "db_config.h"
- #ifndef lint
- static const char revid[] = "$Id: os_map.c,v 11.44 2002/07/12 18:56:51 bostic Exp $";
- #endif /* not lint */
- #ifndef NO_SYSTEM_INCLUDES
- #include <sys/types.h>
- #ifdef HAVE_MMAP
- #include <sys/mman.h>
- #endif
- #ifdef HAVE_SHMGET
- #include <sys/ipc.h>
- #include <sys/shm.h>
- #endif
- #include <string.h>
- #endif
- #include "db_int.h"
- #ifdef HAVE_MMAP
- static int __os_map __P((DB_ENV *, char *, DB_FH *, size_t, int, int, void **));
- #endif
- #ifndef HAVE_SHMGET
- static int __db_nosystemmem __P((DB_ENV *));
- #endif
- /*
- * __os_r_sysattach --
- * Create/join a shared memory region.
- *
- * PUBLIC: int __os_r_sysattach __P((DB_ENV *, REGINFO *, REGION *));
- */
- int
- __os_r_sysattach(dbenv, infop, rp)
- DB_ENV *dbenv;
- REGINFO *infop;
- REGION *rp;
- {
- if (F_ISSET(dbenv, DB_ENV_SYSTEM_MEM)) {
- /*
- * If the region is in system memory on UNIX, we use shmget(2).
- *
- * !!!
- * There exist spinlocks that don't work in shmget memory, e.g.,
- * the HP/UX msemaphore interface. If we don't have locks that
- * will work in shmget memory, we better be private and not be
- * threaded. If we reach this point, we know we're public, so
- * it's an error.
- */
- #if defined(MUTEX_NO_SHMGET_LOCKS)
- __db_err(dbenv,
- "architecture does not support locks inside system shared memory");
- return (EINVAL);
- #endif
- #if defined(HAVE_SHMGET)
- {
- key_t segid;
- int id, ret;
- /*
- * We could potentially create based on REGION_CREATE_OK, but
- * that's dangerous -- we might get crammed in sideways if
- * some of the expected regions exist but others do not. Also,
- * if the requested size differs from an existing region's
- * actual size, then all sorts of nasty things can happen.
- * Basing create solely on REGION_CREATE is much safer -- a
- * recovery will get us straightened out.
- */
- if (F_ISSET(infop, REGION_CREATE)) {
- /*
- * The application must give us a base System V IPC key
- * value. Adjust that value based on the region's ID,
- * and correct so the user's original value appears in
- * the ipcs output.
- */
- if (dbenv->shm_key == INVALID_REGION_SEGID) {
- __db_err(dbenv,
- "no base system shared memory ID specified");
- return (EINVAL);
- }
- segid = (key_t)(dbenv->shm_key + (infop->id - 1));
- /*
- * If map to an existing region, assume the application
- * crashed and we're restarting. Delete the old region
- * and re-try. If that fails, return an error, the
- * application will have to select a different segment
- * ID or clean up some other way.
- */
- if ((id = shmget(segid, 0, 0)) != -1) {
- (void)shmctl(id, IPC_RMID, NULL);
- if ((id = shmget(segid, 0, 0)) != -1) {
- __db_err(dbenv,
- "shmget: key: %ld: shared system memory region already exists",
- (long)segid);
- return (EAGAIN);
- }
- }
- if ((id =
- shmget(segid, rp->size, IPC_CREAT | 0600)) == -1) {
- ret = __os_get_errno();
- __db_err(dbenv,
- "shmget: key: %ld: unable to create shared system memory region: %s",
- (long)segid, strerror(ret));
- return (ret);
- }
- rp->segid = id;
- } else
- id = rp->segid;
- if ((infop->addr = shmat(id, NULL, 0)) == (void *)-1) {
- infop->addr = NULL;
- ret = __os_get_errno();
- __db_err(dbenv,
- "shmat: id %d: unable to attach to shared system memory region: %s",
- id, strerror(ret));
- return (ret);
- }
- return (0);
- }
- #else
- return (__db_nosystemmem(dbenv));
- #endif
- }
- #ifdef HAVE_MMAP
- {
- DB_FH fh;
- int ret;
- /*
- * Try to open/create the shared region file. We DO NOT need to ensure
- * that multiple threads/processes attempting to simultaneously create
- * the region are properly ordered, our caller has already taken care
- * of that.
- */
- if ((ret = __os_open(dbenv, infop->name,
- DB_OSO_REGION | DB_OSO_DIRECT |
- (F_ISSET(infop, REGION_CREATE_OK) ? DB_OSO_CREATE : 0),
- infop->mode, &fh)) != 0)
- __db_err(dbenv, "%s: %s", infop->name, db_strerror(ret));
- /*
- * If we created the file, grow it to its full size before mapping
- * it in. We really want to avoid touching the buffer cache after
- * mmap(2) is called, doing anything else confuses the hell out of
- * systems without merged VM/buffer cache systems, or, more to the
- * point, *badly* merged VM/buffer cache systems.
- */
- if (ret == 0 && F_ISSET(infop, REGION_CREATE))
- ret = __db_fileinit(dbenv,
- &fh, rp->size, F_ISSET(dbenv, DB_ENV_REGION_INIT) ? 1 : 0);
- /* Map the file in. */
- if (ret == 0)
- ret = __os_map(dbenv,
- infop->name, &fh, rp->size, 1, 0, &infop->addr);
- if (F_ISSET(&fh, DB_FH_VALID))
- (void)__os_closehandle(dbenv, &fh);
- return (ret);
- }
- #else
- COMPQUIET(infop, NULL);
- COMPQUIET(rp, NULL);
- __db_err(dbenv,
- "architecture lacks mmap(2), shared environments not possible");
- return (__db_eopnotsup(dbenv));
- #endif
- }
- /*
- * __os_r_sysdetach --
- * Detach from a shared memory region.
- *
- * PUBLIC: int __os_r_sysdetach __P((DB_ENV *, REGINFO *, int));
- */
- int
- __os_r_sysdetach(dbenv, infop, destroy)
- DB_ENV *dbenv;
- REGINFO *infop;
- int destroy;
- {
- REGION *rp;
- rp = infop->rp;
- if (F_ISSET(dbenv, DB_ENV_SYSTEM_MEM)) {
- #ifdef HAVE_SHMGET
- int ret, segid;
- /*
- * We may be about to remove the memory referenced by rp,
- * save the segment ID, and (optionally) wipe the original.
- */
- segid = rp->segid;
- if (destroy)
- rp->segid = INVALID_REGION_SEGID;
- if (shmdt(infop->addr) != 0) {
- ret = __os_get_errno();
- __db_err(dbenv, "shmdt: %s", strerror(ret));
- return (ret);
- }
- if (destroy && shmctl(segid, IPC_RMID,
- NULL) != 0 && (ret = __os_get_errno()) != EINVAL) {
- __db_err(dbenv,
- "shmctl: id %ld: unable to delete system shared memory region: %s",
- segid, strerror(ret));
- return (ret);
- }
- return (0);
- #else
- return (__db_nosystemmem(dbenv));
- #endif
- }
- #ifdef HAVE_MMAP
- #ifdef HAVE_MUNLOCK
- if (F_ISSET(dbenv, DB_ENV_LOCKDOWN))
- (void)munlock(infop->addr, rp->size);
- #endif
- if (munmap(infop->addr, rp->size) != 0) {
- int ret;
- ret = __os_get_errno();
- __db_err(dbenv, "munmap: %s", strerror(ret));
- return (ret);
- }
- if (destroy && __os_region_unlink(dbenv, infop->name) != 0)
- return (__os_get_errno());
- return (0);
- #else
- COMPQUIET(destroy, 0);
- return (EINVAL);
- #endif
- }
- /*
- * __os_mapfile --
- * Map in a shared memory file.
- *
- * PUBLIC: int __os_mapfile __P((DB_ENV *,
- * PUBLIC: char *, DB_FH *, size_t, int, void **));
- */
- int
- __os_mapfile(dbenv, path, fhp, len, is_rdonly, addrp)
- DB_ENV *dbenv;
- char *path;
- DB_FH *fhp;
- int is_rdonly;
- size_t len;
- void **addrp;
- {
- #if defined(HAVE_MMAP) && !defined(HAVE_QNX)
- return (__os_map(dbenv, path, fhp, len, 0, is_rdonly, addrp));
- #else
- COMPQUIET(dbenv, NULL);
- COMPQUIET(path, NULL);
- COMPQUIET(fhp, NULL);
- COMPQUIET(is_rdonly, 0);
- COMPQUIET(len, 0);
- COMPQUIET(addrp, NULL);
- return (EINVAL);
- #endif
- }
- /*
- * __os_unmapfile --
- * Unmap the shared memory file.
- *
- * PUBLIC: int __os_unmapfile __P((DB_ENV *, void *, size_t));
- */
- int
- __os_unmapfile(dbenv, addr, len)
- DB_ENV *dbenv;
- void *addr;
- size_t len;
- {
- /* If the user replaced the map call, call through their interface. */
- if (DB_GLOBAL(j_unmap) != NULL)
- return (DB_GLOBAL(j_unmap)(addr, len));
- #ifdef HAVE_MMAP
- #ifdef HAVE_MUNLOCK
- if (F_ISSET(dbenv, DB_ENV_LOCKDOWN))
- while (munlock(addr, len) != 0 && __os_get_errno() == EINTR)
- ;
- #else
- COMPQUIET(dbenv, NULL);
- #endif
- {
- int ret;
- while ((ret = munmap(addr, len)) != 0 &&
- __os_get_errno() == EINTR)
- ;
- return (ret ? __os_get_errno() : 0);
- }
- #else
- COMPQUIET(dbenv, NULL);
- return (EINVAL);
- #endif
- }
- #ifdef HAVE_MMAP
- /*
- * __os_map --
- * Call the mmap(2) function.
- */
- static int
- __os_map(dbenv, path, fhp, len, is_region, is_rdonly, addrp)
- DB_ENV *dbenv;
- char *path;
- DB_FH *fhp;
- int is_region, is_rdonly;
- size_t len;
- void **addrp;
- {
- void *p;
- int flags, prot, ret;
- /* If the user replaced the map call, call through their interface. */
- if (DB_GLOBAL(j_map) != NULL)
- return (DB_GLOBAL(j_map)
- (path, len, is_region, is_rdonly, addrp));
- /*
- * If it's read-only, it's private, and if it's not, it's shared.
- * Don't bother with an additional parameter.
- */
- flags = is_rdonly ? MAP_PRIVATE : MAP_SHARED;
- #ifdef MAP_FILE
- /*
- * Historically, MAP_FILE was required for mapping regular files,
- * even though it was the default. Some systems have it, some
- * don't, some that have it set it to 0.
- */
- flags |= MAP_FILE;
- #endif
- /*
- * I know of no systems that implement the flag to tell the system
- * that the region contains semaphores, but it's not an unreasonable
- * thing to do, and has been part of the design since forever. I
- * don't think anyone will object, but don't set it for read-only
- * files, it doesn't make sense.
- */
- #ifdef MAP_HASSEMAPHORE
- if (is_region && !is_rdonly)
- flags |= MAP_HASSEMAPHORE;
- #else
- COMPQUIET(is_region, 0);
- #endif
- prot = PROT_READ | (is_rdonly ? 0 : PROT_WRITE);
- /*
- * XXX
- * Work around a bug in the VMS V7.1 mmap() implementation. To map
- * a file into memory on VMS it needs to be opened in a certain way,
- * originally. To get the file opened in that certain way, the VMS
- * mmap() closes the file and re-opens it. When it does this, it
- * doesn't flush any caches out to disk before closing. The problem
- * this causes us is that when the memory cache doesn't get written
- * out, the file isn't big enough to match the memory chunk and the
- * mmap() call fails. This call to fsync() fixes the problem. DEC
- * thinks this isn't a bug because of language in XPG5 discussing user
- * responsibility for on-disk and in-memory synchronization.
- */
- #ifdef VMS
- if (__os_fsync(dbenv, fhp) == -1)
- return (__os_get_errno());
- #endif
- /* MAP_FAILED was not defined in early mmap implementations. */
- #ifndef MAP_FAILED
- #define MAP_FAILED -1
- #endif
- if ((p = mmap(NULL,
- len, prot, flags, fhp->fd, (off_t)0)) == (void *)MAP_FAILED) {
- ret = __os_get_errno();
- __db_err(dbenv, "mmap: %s", strerror(ret));
- return (ret);
- }
- #ifdef HAVE_MLOCK
- /*
- * If it's a region, we want to make sure that the memory isn't paged.
- * For example, Solaris will page large mpools because it thinks that
- * I/O buffer memory is more important than we are. The mlock system
- * call may or may not succeed (mlock is restricted to the super-user
- * on some systems). Currently, the only other use of mmap in DB is
- * to map read-only databases -- we don't want them paged, either, so
- * the call isn't conditional.
- */
- if (F_ISSET(dbenv, DB_ENV_LOCKDOWN) && mlock(p, len) != 0) {
- ret = __os_get_errno();
- (void)munmap(p, len);
- __db_err(dbenv, "mlock: %s", strerror(ret));
- return (ret);
- }
- #else
- COMPQUIET(dbenv, NULL);
- #endif
- *addrp = p;
- return (0);
- }
- #endif
- #ifndef HAVE_SHMGET
- /*
- * __db_nosystemmem --
- * No system memory environments error message.
- */
- static int
- __db_nosystemmem(dbenv)
- DB_ENV *dbenv;
- {
- __db_err(dbenv,
- "architecture doesn't support environments in system memory");
- return (__db_eopnotsup(dbenv));
- }
- #endif